Because in version 6.1 these items are previewed in the context of the page where there are displayed, you have to display them in a page first. After this in Pages where News(Blog Posts) are published
you can choose the preview depending on particular page. For your convenience I have recorded a short video.
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items